Manufacture of balanced motor fuel and aviation safety fuel



Dec. 8, 1942. R. F. MARSCHNER 2,304,187

AND AVIATION SAFETY FUEL MANUFACTURE OF BALANCED MOTOR FUEL Filed NOV. 8, 1939 mskomlu mmmu .Lo NmESu mk v1/wrok I Rober ifMrsc/mer BY@ 7 Arry mw uw Patented Dec. 8, 1942 MANUFACTUBE F BALANCE!) MOTOR FUEL AND AVIATION SAFETY FUEL Robert F. Marschner, Chicago, Ill., assignor to Stnder-fl Oil Company, Chicago', lll., a corpora on o Application November 8, 1939, Serial No. 303,377

's claims. (cl. 19a-so) This'invention relates to the manufacture of motor fuel, aviation safety fuel and high solvency naphtha by processes of dehydroaromatiz- `ation and it pertains more particularly to improved methods for obtaining fuels of properly balanced volatility along with highly aromatic solvency naphtha.

The object of the invention is critically to define the treatment of relatively close-cut naphtha fractions whereby maximum yields of high quality motor and aviation fuels can be obtained with minimum losses to gas and carbon. A further obiect is to provide a method for obtaining a solvency naphtha of higher quality than hitherto obtainable from petroleum products. A further object is to provide an improved method for producing a motor and aviation safety fuel. Other objects will be apparent as the detailed description of the invention proceeds.

If a relatively wide straight-run naphtha cut is subjected to dehydro-aromatization the pentanes and butanes will be partially dehydrogenated, thus increasing the acid heat of the gasoline with which they are subsequently blended and decreasing the lead susceptibility of said fuel.`

The Ca and C1 fractions require more severe or drastic operating conditions than the heavier naphtha fractions and when such fractions are treated together there will necessarily either be insuicient reforming or aromatization of the light fractions or there will be undue degradation of the heavy fractions. Since the heavy fractions yield a considerable quantity of lower boiling hydrocarbons there may be an excess of certain intermediate boiling hydrocarbons. An object of my invention is to overcome these inherent diillculties.

The invention involves the fractionation of the l naphtha into relatively narrow cuts and the subsequent dehydro-aromatization of such cuts under closely defined conditions, particularly with regard to temperature and time factor or space velocity. The pentanes and butanes by-pass the reforming or dehydro-aromatization steps. thereby materially saving in processing costs and improving nished gasoline. The Cs and C1 fractions are dehydro-aromatized with much lower space velocities than have heretofore been used in any commercial operation of this sort; such space velocities may range from 0.05 to 0.5 volume of feed per volume of catalyst space per hour and the temperature is preferably about 900 to 1000" I'. The intermediate naphtha fraction, which would be primarily the C: or the C1- same conditions as the Ca-C'z fraction but as hereinafter pointed out. this fraction is converted almost quantitatively to aromatica and yields a solvency naphtha which is markedly superior to any heretofore produced from petroleum products. The heavy naphtha fractions, preferably C9 to C14 hydrocarbons. are treated under such conditions that aromatization may be supplemented by cracking, but I have found that in the treatment of this fraction higher space velocities should be employed, particularly with temperatures as high as 950 to l000 F. The space velocity for such fraction should be at least 0.6 and preferably about 1 to 3 volumes of liquid feed pe volume of catalyst space per hour.

A feature of the invention is the removal of the intermediate naphtha fraction from' those components which eventually go to form the flnished motor fuel and aviationsafety fuel. The safety fuel fractionated from dehydro-aromatized heavy naphtha is characterized by high total heat content, relatively low acid number, high octane number and good lead rponse. The more volatile components obtained by the dehydro-aromatization of heavy naphtha are blended with the aromatized Cs-Cv fraction and with the unaltered butanes and pentanes to make a high octane motor fuel of excellent volatility.

It should be specifically noted that the Cs fraction obtained from the dehydro-aromatization of heavy naphtha because ofthe thermal instability of the later contains appreciably more open chain C1 and Cs hydrocarbons than the aromatized products from the treatment of the original C'z-Ca fraction which undergoes a particularly clean reaction. In other words, by removing the intermediate naphtha fraction for the preparation of solvency naphtha a more highly aromatic naphtha is obtained than could possibly be secured by introducing all treated products into a common fractionator and obtaining the solvency naphtha cut from that fractionator. The C1 and Cs hydrocarbons obtained by the conversion of the heavy naphtha fraction are somewhat less desirable in solvency naphtha but they are excellent components for motor fuel or aviation gasoline.

The invention will be -more clearly understood from the following detailed description read in connection with the accompanying drawing which is a simplified diagrammatic ow sheet illustrating my improved process. f

My invention is not limited to any particular naphtha. The naphtha may be either straight- Cs fraction is aromatized Tmder substantially the run or cracked or it may be produced by the hy.

drogenation of carbonaceous materials, by the catalytic conversion of carbon monoxide and hydrogen or by any other known method. In the preferred embodiment of the invention I will describe the conversion of straight-run -naphtha from East Texas crude. Preferably the original naphtha is a straight-run or paraiinlc naphtha with a relatively low octane number.

'Ihe catalyst employed for the reforming or dehydro-aromatization steps is preferably an oxide of a VI group metal mounted on active alumina or alumina gel. About 2 to 10% of molybdenum oxide on alumina .or about 8 to 40% of chromium oxide on alumina have been found to give excellent results. It should be understood, however, that the present invention is not limited to any particular catalyst but is applicable to the use of any dehydro-aromatization catalyst known to the art. 'Ihe minor ingredient of the catalyst is preferably an oxide or sulde of molybdenum, chromium, tungsten or uranium or any admixture thereof mounted on bauxite, precipitated alumina, Activated Alumina or any other suitable catalyst support. Magnesium, aluminum or zinc chromites, molybdenites, etc. may also be employed. Vanadium and cerium oxides have likewise been found to be effective for this conversion. Oxides of copper. nickel, manganese, etc. may be included to facilitate regeneration or to supplement or promote catalyst activity.

'I'he catalyst may be made by impregnatlng activated alumina or other support with molybdic acid, ammonium molybdate or any other catalyst compound decomposable by heat. Also the aluminum and molybdenum oxides may be co-precipitated as a gel or the separate oxides may be mixed together as a paste, dried, extruded under.

pressure or pelleted and heated to a temperature of about 1000 to 1200 F. Since the preparation of catalyst forms no part of the present invention it will not be described in further detail.

The catalyst may be employed in fixed beds, in movable beds or as a powder suspended in a vaporous stream, the conversion in all cases being in the vapor phase. The fixed bed catalysts may be positioned in tubes mounted for instance in the convection section of a furnace or they may be positioned in a single bed or plurality of beds in vertical towers or chambers. The moving catalyst may be charged to the top of a tower or tube either continuously or intermittently, the spent catalyst being withdrawn from the base of the tube at substantially the same rate; in this case the reaction takes .place continuously and under substantially constant conditions of temperature and pressure, the regeneration being effected outside of the conversion zone. The powdered catalyst may be fed into a rapidly moving stream of vaporized naphtha and hydrogen, separated therefrom after reaction is completed and separately regenerated by oxygen while suspended in flue gas. Any of these specific catalyst' reactors or their equivalents may be used in practicing the invention, but they will not be described in further detail.

Referring specifically to the drawing, a wide cut East Texas naphtha is passed from a heater (not shown) through line I to fractionator I l from which propane and lighter gases are removed overhead through line i2, pentanes and butanes `are removed as a side stream through line I3 to receiver I4, Ce and C1 hydrocarbons (herein called light naphtha) are withdrawn through line Il to receiver I6. C1 and Ca hydrocarbons .(herein called intermediate naphths) are withdrawn through line Il to receiver it, C to C14-hydrocarbons 75 (herein called heavy naphtha) are withdrawn through line i8 to receiver 20 and gas oil is removed through line 2i.

While I refer to Ce-C-r hydrocarbons, Cr-Cn hydrocarbons, etc. it should be understood that close fractionation is not essential in the practice oi' my `vinvention. The light naphthal fraction may contain some pentanes and even a small amount lof octanes, and the intermediate fraction which preferably consists chiefly of octanes, may contain considerable amounts of heptanes with perhaps some lighter and heavier hydrocarbons. In other words, some overlapping isof no serious consequence, but for obtaining maximum advantages of the invention the fractionation should be as sharp as is economically feasible.

The light naphtha fraction is passed by line 22 and pump 2l through coils 24 of furnace Il and adxnixedwith hydrogen introduced through line 2l and heated incoils 21. Preferably about 0.5 to 8 mols of hydrogen are used for each mol of hydrocarbon stock undergoing aromatization and the pressure is of the order of 30 to 450 pounds per square inch, for example about 200 pounds per Square inch. The hot vaporized lisht naphtha mixture is then introduced through line 28 to conversion chamber 2l and therein contacted with' catalyst at a temperature of about 900 to 1000 F., for example about 975 F. allowing a much longer time of contact than is usually permitted for total naphtha reforming. The space velocity in conversion chamber 20 should be about 0.05 to 0.5 volume of liquid feed per volume of catalyst space per heur. Temperatures as high as 1025 F. may be employed but unduly high temperatures may result in cracking. Such cracking is highly undesirable because the hydrocarbons are already among the lighter components of gasoline and if they are converted into still lighter products they will fall outside of the gasoline boiling range, i. e. there will be unduly high gas losses. An important feature of the invention is the treatment of this light naphtha fraction at only a moderately high temperature but with a very low space velocity. In other words the severity of the treatment is obtained by increasing the time of contact or the time factor rather than by employing extremely high temperatures.

'I'he products from reaction chamber 29 are withdrawn through line II to hydrogen separator 3| which is preferably operated at about reaction pressure and at a temperature of about 35 to 105 l". Hydrogen is recycled through 4line Sla and the liquid products are withdrawn throughline I! to receiver 33.

'I'he intermediate naphtha fraction is introducted by line ll and pump I5 to coils 3l of furnace 3l. About 0.4 to 8 mols of hydrogen per mol of naphtha are introduced through line 3l to coil 3l and the hot mixture is then passed by line 4l to conversion chamber 4I. In this chamber it is desired to obtain as nearly a quantitative conversion to aromatics as possible. Here again the temperature may range from about 900 to 1000 F., for example about 950 to 975 F'. and the space velocity should be about 0.05 to 0.5 volume Yof charge per volume of catalyst space per hour, the pressure conditions being the same as for reaction chamber 2l. Products from chamber Il are withdrawn through line I2 to separator 4l, the hydrogen being recycled through line Il and the liquid products withdrawn through line 45 to receiver l0. These products are highly aromatic and may be employed without further fractionation as high quality solvency naphtha.

' version process.`

acterized by a very high octane number.

f ,sofaiev 4The heavy naphtha fraction "is chargedby line' 4l and pump 48 to coils 49 of furnace 50. Hydro.- gen from line 5| is heated in coil 5 2, the same amounts of hydrogen and the same reaction pressures being employed as hereinabdve described.-

in order to avoid undue amounts of cracking the temperature should not exceed 1025 F. and should butanol mixture-it measures the solvent power of the naphtha for kauri'gum). A 'grade 2 high preferably be below 1000 F. yTemperature.; of

about 900 to 975 F. constitute the preferred range, for example about 950 F., it being understood that the higher the temperature, the. lower thecontact *time for obtaining equivalent conversion.

The conversion products from reactor 54 are withdrawn through line 55 to hydrogen separator 55, the hydrogen being recycled through line 51 o y and the products withdrawn through line 58 to receiver 59.

With proper catalysts and operating conditions I it should be unnecessary to supply hydrogen from' external sources but should additional hydrogen `be required it may be introduced through line $0 to lines 5I, 38 -or 25.' Excess hydrogen produced in the system maybewithdrawnthrough line 5I Certain advantages of the invention may be accomplished without the use of hydrogen at all but its use is highly desirable andit-hastherefore been described in .connection with theprefuel may be' withdrawn as a side cut through line 66 and hydrocarbons boiling above the safety fuel boiling range may be withdrawn through line 61 and combined with the gas oil from line 2| for thermal or catalytic cracking or other con- An exceptionally high quality m'otorf'fuelof high volatility and high octane number is'. produced by blending pentane and butanes from receiver I4 and line 6 8 'with aromatizedvC andlCr hydrocarbons from receiver 33 and lline 6 9 and with the light ends leaving `fra'ctionator 64 through line 65. The Ca-Cio hydrocarbons leaving fractionator 64 contain more branched op'en chain hydrocarbons than` are present in the products in receiver 45. Thus while they do not constitute as high quality solvency naphtha as that produced by the dehydro-aromatization of the intermediate fraction, they provide the necessary intermediate and heavy ends for a balancedmo- .tor vfuel and the resulting motor fuel char- The boiling range of -the solvency naphtha will depend on the sharpness of the fractionation of the original intermediate naphtha or, of course,

"the solvency naphtha may be separated into various grades by subsequent distillation. A grade 1 high solvencynaphtha may, for instance, vhave a boiling range of 203 to 283 F. an aniline point lower than 28 F. and a number higher than 86. (The kauri number is the number of cc.'s of the naphtha miscible with 20 grams of a 16%% (by weight) solution of kauri gum in solvency naphtha may have a boiling range between '275 .and 356 F., an aniline point below 36 F. and a kaurrnumber in excess of 87.

The safety aviation fuel should have an initial boiling' point of about 330 F. and an end point of about 420 F. with'a minimum flash of about 110 F. Its acid heat should be not higher than- 20 F.

The high octane motor fuel should have an initial boiling point of at least 131 F. and an end point 0f about 400 F. With 10% Over' at 167 F., at 284 F. and'90% at about310 tov While I have described 'a preferred vembodiment of my invention it should be understood that I do not limit myself to the details or specic conditions described since many modifications and changes will be apparent to those skilled in the art. For instance, the separate naphtha fractions may be segregated and subsequently processed, one at a time, in a single reactor. 'the conditions being maintained in the reactor for each fractiondn accordance with the conditions.

hereinabove described.

I claim: 1. The method of making high octane number gasoline and aviation safety fuel from relatively low octane number naphtha, which comprises fractionating said naphthal into light, intermediate and heavy fractions, respectively, contacting said light naphtha fraction 'with a dehydroaromatiz'ationcatalyst at a temperature of-about v 900 to 1000 F., with a, space velocity of about 0.05 to 0.5 volume of liquid feed per volume of catalyst space per hour, contacting the heavy naphtha fraction with a dehydro-aromatization catalyst at a temperature of about 900 to 1000 F. with a space velocity of about 0.6 to 2 volumes of liquid feed per volume of catalyst space per hour, fractionating the dehydro-aromatized heavy naphtha into an aviation safety fuel fraction and a light fraction and blending said light fraction with dehydro-aromatized light naphtha t'o form high octane number gasoline.

2. The method of claim 1 which includes the further step of separating the original naphtha feed into a pentane fraction as well as light,

intermediate and he'avy fractions and which includes the further' step of blending separated pentane with the dehydro-aromatized light naphtha fraction and with the light fraction of dehydro-aromatized heavy naphtha for the production of high octane number gasoline.

3. The method of obtaining high octane number motor fuels from a relatively low knock rating naphtha with a wide boiling range which comprises fractionating said naphtha into a light, intermediate and heavy fraction, respectively, separately dehydro-aromatizing the intermediate naphtha fraction under conditions for obtaining maximum conversion to aromatics, dehydro-aromatizing the heavy naphtha fraction under conditions for effecting both cracking and aromatization whereby hydrocarbons of intermediate boiling range' are obtained, and blending unconverted hydrocarbons of said light fraction with at least a part of the aromatized hydrocarbons from the intermediate fraction and at least a part of the intermediate boiling range hydrocarbons from said heavy fraction for producing -a balanced high octane number gasoline.

4. The method of making high quality motor fuels from low knock rating naphtha which comprises separating said naphtha into a light i and heavy fraction, respectively, catalytically deof liquid charge per volume of catalyst space per hour, blending light components of the products from the dehydro-aromatization of A,heavy naphtha with the products. produced by the dehydro. ,a-romatization of light naphtha for the produciion of a high octane number motor fuel having an initial boiling point of at least 131 F., an end point of about 400 F., a 10% distillation point of aboutv 167 F., a 50%v distillation point at about 284 F. and a 90% distillation point of about 310 to 350 F.

5. In a process fo'x` obtaining 'aromatics and high octane number gasoline from a relatively low knock-rating naphtha the method of operation which comprises fractionating the low knock-rating naphtha into light, intermediate and heavy fractions respectively, contacting said iight naphtha fraction with the dehydroaromatization catalyst at a temperature of about 900 to 1000 F." with a space velocity of .05 to 0.5 volume of liquid feed per volume of catalyst space per hour, contacting the heavy naphtha fraction with a'dehydroaromatizationcatalyst at a temperature' of about.900 to 1000 F. with a space F. with a space velocity'of about I to 3 volumes velocity of about .6 to 2 volumes of liquidieed per volumeof catalyst space per hour, fractionating 'the dehydroaromatiz'ed heavy Inaphtha into a gasoline fraction and a heavier fraction andblending said gasoline fraction with dehydro` aromatized light naphtha to form high octane number gasoline.

6. 'I'he method of producing'higl'roctane'iium-l ber motor fuels from a relativelyA low knock rating naphtha of wide boiling range which method comprises fractionating said naphtha into a plurality of fractions including a light naphtha fractionjan intermediate fraction and a heavy naphtha fraction, contacting said light naphtha fraction with a catalyst under such conditions as to materially increase its octane number, contacting said heavy naphtha fraction with a der l hydroaromatization catalystat space velocities and temperatures for eiecting both cracking and aromatization whereby the hydrocarbons in. said fraction are converted intohydrocarbons of lower boiling range intermediate the boiling range of said light naphtha fraction .and said heavy naphtha fraction; said hydrocarbons of lower boiling range replacing said intermediate fraction which' is not treated for addition to the high octane number gasoline product, fractionating the de hydroaromatization products into a gasoline fraction and a heavier-,fraction and ,blending said gasoline fraction with the high octane number products produced from said light naphtha fraction for making. a high ,octane number gasoline.

ROBERT F. MARSCI-INER. 

